Integrated circuits are formed in wafers of semiconductor materials, such as silicon or compound semiconductors such as GaAs, GaN and the like. The wafers are processed in fabrication clean rooms with processing and handling equipment of a limited size. Thus, there is a maximum upper limit on the size that integrated circuits can have, for example a 450 mm diameter. Similarly, although wafers are diced into small integrated circuits, for example with a diamond saw, there is a lower limit on the size of integrated circuits that can be readily physically handled, for example surface mountable devices having a size of 0.4 mm by 0.2 mm.
Large flat-panel displays typically rely on thin-film semiconductor structures coated on display substrates to provide control signals that control pixels in large-substrate flat-panel displays, for example a 65-inch diagonal rectangular display. However, such thin-film structures have relatively low performance when compared to crystalline semiconductor structures typically used in integrated circuits.
Micro-transfer printing is an alternative method for assembling small high-performance integrated circuits onto large substrates including, but not limited to, for display applications. Micro-transfer printing relies on forming small integrated circuits (chiplets) on a source wafer substrate and then, in one exemplary technique, using silicone elastomer stamps to transfer the chiplets to a target destination substrate, for example as described in U.S. Pat. No. 9,434,150 entitled “Apparatus and Methods for Micro-Transfer-Printing” and issued Sep. 6, 2016. The target destination substrate can range in size from tens of microns to several meters in a dimension. In any micro-transfer printing process, the efficiency and yields of the transfer process are important. For example, the above-referenced U.S. patent describes exposing the transferred integrated circuits to a plasma to improve transfer. However, further improvements in micro-transfer printing yields and efficiency are useful.
There is a need, therefore, for devices, systems and methods for enabling micro-transfer printing with high efficiency and yield.